In many instances, it is necessary to transfer an object to a treating station at an inaccessible location. For example, in film processing under vacuum conditions, an object to be coated, such as a substrate, must be transferred between the exterior and interior of a vacuum enclosure. Typically, the substrate is fixedly mounted on a substrate holder that is carried into the vacuum by a carriage and is transferred between the carriage and a treating station, where films are deposited on the substrate.
For certain applications, such as molecular beam epitixial coating, it is necessary to maintain the substrate at a precisely controlled, elevated temperature. Typically, thermocouple junctions are utilized to monitor the temperature of the substrate. In one prior art arrangement, the thermocouple junctions were formed by fusing wires of dissimilar metals into a bead which in turn was in contact with the substrate holder. The transferring of the holder has been found to cause the junctions to wear, bend and in the case of brittle materials, fracture because of friction between them and the substrate holder. Further, the temperature of the bead itself is measured and the generally relatively marginal thermocontact between the bead and holder results in reduced accuracy and reproducibility. The wire wearing problem is particularly severe in molecular beam epitixial deposition, a process that is performed in an ultra high vacuum, on the order of 10.sup.-10 torr. Of course, in ultra high vacuums, there are few gas molecules between the contacting surfaces and the frictional problems are severe when parts rub together.
Another problem that can occur is that radiant energy from a substrate heater, controlled by the thermocouple, can propagate to the thermocouple and cause the thermocouple to derive a voltage that is not accurately related to the substrate temperature. This is particularly severe in the case of beaded thermocouples.
It is, accordingly, an object of the present invention to provide a new and improved apparatus for monitoring the temperature of an object, that can be transferred from a carriage to a treating station, while the object is located at the treating station.
A further object of the invention is to provide a new and improved mechanism for transferring an object between a treating station and a carriage.
Another object of the invention is to provide a new and improved apparatus for accurately and reproducibly monitoring the temperature of a substrate located at a treating station in a vacuum enclosure, which substrate is selectively brought to the testing station by a carriage device.
An additional object of the invention is to provide a new and improved apparatus for transferring an object from a carriage to a treating station in a vacuum and for monitoring the temperature of the object by means of thermocouples that are not subject to mechanical wear during the transfer. and which yield more accurate, reproducible measurements.
Yet another object of the invention is to provide a new and improved apparatus for transferring an object from a carriage to a treating station that includes a heater for the object, as well as a monitor for the temperature of the object, wherein radiant energy from the heater is shielded from the temperature monitoring apparatus.